Liverpool could be the best team for Mane. He's had the best years of his career there, Bayern hasn't been so good for him. There is already a long expectation that he will return to England. If he is going to play in the Premier League, he can come to Liverpool and make an effort to make the team champion again.
I don't think it is possible for Sadio Mane to play for Liverpool again, the club has already moved on after his exit, so they would be better off signing new players and try to build a team around them, rather than bringing back players who gave their best to the team and have already left for a different challenge. Sadio Mane didn't have the best first season in Bayern Munich, but i don't think he is ready to leave just yet, i know that the altercation with Leroy Sane makes it somewhat tricky as the club might want to sell one of them, which would prolly be Mane, but since the transfer window opened, there've been no news on Mane leaving the German champions.
Exactly because of his performance last season Liverpool wouldn't sign him again in their craziest dreams. That is not going to happen and even though I like Mane as a player a lot and he was the perfect complementary player in the offense for Liverpool, he doesn't really have versatile qualities that make him valuable in games that require some flexibility.